In recent years, displays have come to be widely varied in the principles thereof. One which is currently being given much attention is the plasma display, which enables larger sizes that are thin and with reduced weight, as compared to conventional cathode-ray tubes. With this, electric discharge is generated in a discharge space formed between a front plate and a rear plate, and ultraviolet light primarily around 147 nm is generated from xenon gas due to this discharge, thereby enabling display by the ultraviolet light causing excitation of fluorescent substance. Full-color display can be handled by a driving circuit causing light emission of discharge cells wherein fluorescent substances have been separately applied for red (R), green (G), and blue (B).
Also, with AC type plasma displays regarding which development is recently being actively pursued, a front glass plate having formed thereupon display electrodes/dielectric layer/protective layer, and a rear glass plate having formed thereupon address electrodes/dielectric layer/barrier rib layer/fluorescent substance layer, are applied one to another, and a mixed gas of He-Xe or Ne-Xe is sealed in the discharge space sectioned off by stripe-shaped barrier ribs.
Each of the R, G, and B, fluorescent substance layers have recesses of rough portions formed by barrier ribs extending in one direction for each color, formed on the rear plate, being filled in a stripe-like manner with a fluorescent substance paste having powder-like fluorescent substance particles as the primary component thereof.
Striped black matrix color picture tube panels also have the structure wherein the fluorescent substance is configured in stripes.
Manufacturing such configurations with high productivity and high quality requires technology for separately applying fluorescent substance in constant patterns.
For example, Japanese Unexamined Patent Application Publication No. 10-27543 (U.S. Pat. No. 5,921,836) discloses a method for applying between barrier ribs on a plasma display panel with an application die.
With this die, multiple discharge orifices are bored in a generally straight line with constant spacing therebetween, and an application fluid reservoir is provided within the die.
Also, an application fluid supplying opening for supplying application fluid to the application fluid reservoir is provided at the upper part of the die.
With such a die, the internal pressure of the application fluid reservoir rises upon application fluid being supplied from the application fluid supplying opening, whereby a predetermined amount of application fluid is discharged from the discharge orifices, and application fluid is applied onto the surface of the base material.
However, with a die such as described above, in the event that application fluid is supplied to the application fluid reservoir and the internal pressure of the application fluid reservoir repeatedly rises, there is the risk of the die being pressed open and deformed. Particularly, with dies of a long and narrow shape wherein a great number of discharge orifices are arrayed, the area receiving pressure is great, and accordingly deformation readily occurs. In the event that the die is deformed, there is the possibility that the discharge orifices may also be deformed, causing irregularities in the amount of application fluid discharged and so forth, so there is the risk that application fluid may not be applied to the surface of the base material uniformly. Also, there is another form of the die wherein the member forming the discharge orifices and the member forming the application fluid reservoir are separate members, which are connected by tightening with bolts, by welding, or by adhesion, but in this case, shearing force acts on the connecting face due to the deformation of the die, so there is the possibility that both members peel away, and the die is destroyed. Incidentally, making the components of the die thicker in order to improve pressure-resistant strength within the die contradicts the direction of reduction in weight and reduction in costs of the die and also the application apparatus.
Also, this die has an application fluid reservoir and space above the application fluid within, and a structure is necessary wherein pressurized air is injected to this upper space so as to press the application fluid out from the die by this pressure. The reason is that with a structure wherein application fluid is filled in the die and a constant amount is pumped with a pump or the like, the amount of pressure loss in the piping of the application fluid is great in the event that the viscosity of the fluorescent substance paste which is the application fluid is great, and delay in starting application becomes marked.
Also, with a die having space at the upper part of the application fluid, there is the need to supply the same amount of fluorescent substance paste that has been applied to within the die again, following application of the fluorescent substance paste to the base material which is the object of application.
However, with the application of application fluid such as disclosed in the aforementioned Japanese Unexamined Patent Application Publication No. 10-27543, there are the following problems.
That is, at the time of supplying the fluorescent substance paste to within the die, applying a method wherein the fluorescent substance paste is simply allowed to free-fall from above the die risks bubbles being mixed into the fluorescent substance paste. In the event that bubbles are mixed in, there is a break in the paste discharged at the point that the bubble emerges from the discharge orifice of the die, resulting in faulty application.
Also, at the time of supplying the fluorescent substance paste to within the die, supplying from one place requires too much time. Also, in the event that the fluorescent substance paste has high viscosity, time is required for the fluid level within the die to become flat.
Also, the amount of fluorescent substance paste discharged from the die is determined by the sum of the head of the fluorescent substance paste pooled within the die and the pressure of the pressurized air supplied to the space above the fluorescent substance paste, so there is the need to maintain the fluid level of the fluorescent substance paste constant, in order to maintain the amount of discharge constant.
Particularly, in the event of using a die having multiple discharge orifices, irregularities in the amount of discharge from the discharge orifices occurs unless the fluid level of the fluorescent substance paste is maintained constant and flat, thereby resulting in irregularities in application, and so forth. Accordingly, application fluid is preferably supplied to within the die from multiple application fluid supplying openings.
However, it has been found that supplying application fluid from multiple application fluid supplying openings risks occurrence of application irregularities. According to studies made by the Inventor of the present Application, it has been found that fluorescent substance paste supplied from multiple application fluid supplying openings always merge and pool at a certain position within the die, and that fluorescent substance paste discharged from the discharge orifices near this merging point cause the application irregularities.
That is to say, at the time of supplying fluorescent substance paste to the die, shearing stress such as that which acts while flowing through tubes and the like acts upon the fluorescent substance paste. High-viscosity paste such as the fluorescent substance paste is subject to change in viscosity due to the magnitude and time of the shearing stress. Part of the fluorescent substance paste supplied into the die having been subjected to shearing always reaches the merging position and pools.
The fluorescent substance paste at the merging point differs from the fluorescent substance paste at other parts with regard to the magnitude of the shearing stress and the time of acting thereof, and accordingly, the viscosity is markedly changed as to fluorescent substance paste at other parts. At the time of pressurizing the fluorescent substance paste for discharging from the discharge orifices, there is a correlation between the amount of discharge and the paste viscosity under the same pressure, and consequently, the amount of fluorescent substance paste discharged from the discharge orifices near the merging position differs from that at other parts, thus causing faulty application such as irregularities in application.
Also, in the field of plasma displays in recent years, in order to answer the demand for improved brightness and contrast and conservation in electric power consumed, a base material 100 is being employed wherein horizontal barrier ribs 102 which generally orthogonally intersect vertical barrier ribs 101 extending in the direction of application of application fluid as shown in FIG. 1 (in the direction of the arrows in FIG. 1) and which are lower than the vertical barrier ribs 101, are formed (e.g., Japanese Unexamined Patent Application Publication No. 11-213896, Japanese Unexamined Patent Application Publication No. 2000-123747, etc.). With such a base material 100, horizontal barrier ribs 102 are disposed between the vertical barrier ribs 101, so the grooves 110 of the barrier ribs 101 are formed with a lattice-like shape, having recesses 103 and 104.
Also, with the above-described application method for application fluid, the application fluid 108 containing fluorescent substance is applied to the grooves 110 and then dried and hardened to form the fluorescent substance layer, but with light-emitting substrates for plasma displays, the discharge generated between the barrier ribs 101 must be allowed to efficiently act and the light emitted at the fluorescent substance must be efficiently extracted in order to perform suitable light emission between the barrier ribs 101. As a form of the fluorescent substance layer to that end, the fluorescent substance layer preferably exists over a wide range on the entire face of the wall faces of the barrier ribs 101 and the base of the grooves. Accordingly, the application fluid 108 is preferably applied so as to fill up the grooves 110.
However, using the application apparatus and the method thereof for applying application fluid to conventional base material having striped grooves, for applying application fluid to base material having lattice-shaped grooves, without any change, risks the following problems. That is to say, as shown in FIG. 2, in the event of applying the paste-state application fluid to the grooves 110 formed between each of the vertical barrier ribs, the application fluid discharged from the discharge orifice 106 of the die 105 must cross over the horizontal barrier rib 102, but the clearance between the apex of the horizontal barrier rib 102 and the face 109 of the discharge orifice formation plate 107 which has the discharge orifice 106 of the die 105 becomes small, so there is the risk of the application fluid (paste) 108 coming into contact of the face 109 of the discharge orifice formation plate 107, as indicated by the dotted line in FIG. 2. Once the application fluid becomes adhered near the discharge orifice 106 of the discharge orifice formation plate 107 during application, the application fluid discharged from the discharge orifice 106 is drawn to that point, so discharging actions are disturbed, and there is the risk of skipped application portions wherein the application fluid is not applied to the groove 110, which are so-called isolated spots.
Accordingly, it is an object of the present invention to provide a die with improved pressure-resistance while dealing with requests for reduced weight and reduced costs, and to provide an application apparatus and application method for application fluid and a manufacturing apparatus and manufacturing method for a base material for a plasma display, wherein application fluid can be uniformly applied to the surface of the base material by employing this die.
Also, in light of the various problems as described above, it is an object thereof to provide a die wherein application fluid is discharged from multiple discharge orifices and no discharge irregularities occur thereby, and an application apparatus and application method using the die, and particularly an application apparatus and application method enabling application in a desired uniform manner at the time of applying fluorescent substance paste of a high viscosity from the application die to multiple recesses of a base material wherein a constant uneven pattern is formed such as with barrier ribs of plasma display panels.
Also, it is an object thereof to provide an application apparatus and application method for application fluid and a manufacturing apparatus and manufacturing method for a base material for a plasma display panel, wherein application skipping (isolated spots) is prevented even upon application of application fluid to the base material with lattice-like grooves formed on the surface thereof, so as to allow desired paste patterns to be drawn and formed on the surface of the base material in a sure manner.